A. Field of the Invention
The invention relates generally to human-powered transportation and specifically to recumbent vehicles.
B. Description of Related Art
Bicycles have become a common mode of human-powered transportation. In conventional so-called upright bicycles, such as multi-speed racing bicycles and mountain style bicycles, the seat is positioned between and above the wheels while, the pedal assembly is positioned essentially vertically downward from the scat.
Conventional so-called upright bicycles suffer from a set of drawbacks. One of the main drawbacks associated with the so-called upright bicycles is that a relatively high proportion of the effort expanded by the rider is used to overcome wind resistance. Another drawback of the conventional upright bicycles relates to the fact that the rider sits relatively high away from the ground and that in the event that a high degree of deceleration is achieved, the rider may be projected forwardly. Furthermore, hard braking can also lead to severe skidding of the tires. A still further drawback of the conventional so-called upright bicycles is the general lack of ergonomic characteristics associated with the rider's position. An upright bicycle is also difficult to balance when at rest and the rider typically has to lower his or her foot to balance the bicycle. When carrying cargo on the frame itself, the upright bicycle becomes all the more unstable in motion as the added weight shifts from side to side.
In order to overcome the above-mentioned disadvantages, another type of human-powered transport has evolved throughout the years, namely the so-called recumbent tricycle. A recumbent tricycle differs from a conventional upright bicycle in that the rider sits behind the foot pedals in a recumbent or reclining position on a seat that is usually provided with a backrest, and the tricycle has three wheels (although some recumbent have a 2 wheel version). The recumbent tricycle may have two wheels in front and one in the rear, known as a “tadpole” design, or two wheels in the rear and one in the front, known as a “delta” design.
Unlike in an upright bicycle in which the rider's legs extend generally downwardly, in a recumbent tricycle, the rider's legs extend forwardly substantially parallel to the ground. As such, the combined frontal area of a recumbent tricycle and rider is typically substantially less than in a conventional upright-type bicycle, thus causing less wind resistance.
Furthermore, a lower center of gravity, greater tire contact due to three wheels and a feet-forward riding position mean that a higher degree of deceleration can be achieved without the rider being projected forward, as he or she might on a conventional bicycle. The risk of injury to the body due to contact with the handlebars, brakes and gear shift levers is reduced in the event that the rider is thrown forward. The feet being positioned in front of the rider, they are most likely to make contact in a head-on collision, often bracing the rider and preventing substantial injury. The rider rarely goes over the handlebars, resulting in fewer head injuries, and the low centre of gravity means the rider has a reduced distance to fall before contacting the ground.
Moreover, during pedalling, the loads applied to the rider's body against the seat in reaction to the forces applied to the foot pedals by the rider's legs are transmitted to the seat through the hips and shoulders of the rider, similar to the effect of a contact point on a lever. This enables the upper torso and arms of the rider to remain relaxed while full power is being applied to the foot pedals.
Furthermore, the seat of a recumbent tricycle typically supports more of the rider's body area, including his back, so that the weight of the rider is distributed over a larger surface for greater comfort. This may also be more suitable for people with balance or limb disabilities. Also, the recumbent position allows for greater thrust power since the back of the rider can be braced against the seat. In an upright bicycle, the maximum thrust is limited by the weight of the rider, although this can be helped if the rider pulls up on the handlebars while pushing down on the pedals.
Finally, and with particular reference to the present recumbent tricycle, the seat of recumbent tricycle can be supported by way of pivot joints such that said seat moves semi-independently to the remainder of the recumbent tricycle chassis. In this instance, the centrifugal force as experienced by the driver is lessened as said driver can move, to a certain extent, in the same direction as the centrifugal force. Further, the resulting suspension of the recumbent tricycle's seat is better suited to absorb shock resulting from debris or imperfections on the road.
A recumbent tricycle in the delta configuration, with two rear wheels and one front wheel, has some specific advantages relative to the tadpole configuration, such as the possibility of an expanded cargo capacity.
Although recumbent tricycles have been the subject of previous patents and patent applications, some of the prior art recumbent designs suffer from a further set of drawbacks. For instance, U.S. Pat. No. 6,062,581 describes a recumbent tricycle in a delta configuration, in which only the front wheel turns in the direction in which the rider would like to go, and the front portion of the frame remains in a forward orientation. This type of steering is unstable when cornering at higher speeds because the front portion of the frame is unable to lean into the turn.
Another example, U.S. Pat. No. 4,826,190 discloses a tricycle in a delta configuration, with rear-wheel drive and a fork-mounted front wheel that pivots by means of turning the fork. A rear-wheel drive mechanism for a tricycle in a delta configuration is complex, expensive and requires heavier hardware. For instance, it will require a full axle to transmit power to both wheels, and a differential gear, for example, to permit the wheel on the outside of the turn radius to turn faster than the wheel on the inside of the turn radius. It will also call for a longer drivetrain to transfer power to the rear from the front crankset.
Yet another example of the prior art, U.S. Pat. No. 4,456,277 discloses a tricycle in a tadpole configuration, with the two front wheels serving as the drive wheels. Again, this type of configuration requires a differential which adds cost, and it is more difficult to get into and out of than a delta configuration. The tadpole configuration also does not offer an obvious way to store and carry cargo.
In another patent, U.S. Pat. No. 4,432,561 discloses a two-pivot tricycle in delta configuration, which contains a center joint so that the seat, pedals and front wheel pivot in the direction in which the rider would like to travel. The pivot disclosed is comprised of a cam bearing, wedged in between a pin and a housing. Unfortunately, said pivot system cannot provide for an efficient inclination as the cam bearing has very little give and the tubes constitute welded pieces one onto another. In other words, the more stressed the system becomes, the more pressure that will result on the overall tricycle's chassis.
Finally, U.S. Pat. No. 4,572,535 discloses another type of two-pivot tricycle, wherein said pivot is comprised of a bolt, pivotally fastened on one end to a bolt hole, and on the other end to a nut. In between said bolt hole and nut lies a spacer, whereby when side to side movement occurs on the tricycle, the bolt can pivot around the bolt hole, and compresses the spacer on either side, depending on the movement in order to compensate for said movement. However, depending on the size and suppleness of the spacer, the tricycle is restricted in terms of movement. Further, the spacer-style pivot is not an appropriate substitute for a proper coil or spring suspension to create a comfortable experience for riders.